The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

ALP demands Heydon show Lib speech invite

Opposition Leader Bill Shorten says he will continue to cooperate with the Royal Commission into union corruption.

But he has repeated demands for the release of all correspondence between commissioner Dyson Heydon and organisers of a Liberal Party fundraiser.

Mr Heydon has withdrawn from the August 26 speech, telling organisers that if there was any possibility it could be described as a Liberal Party event he couldn't do it while presiding over the royal commission.

"I think that for many Australians the fact that Mr Heydon was billed as a guest speaker at a Liberal Party fundraiser is the smoking gun of political bias," Mr Shorten said on Friday.